Carbon and columbium containing nickel alloys



United States Patent C) 3,303,022 CARBON AND COLUMBIUM CONTAINING NICKELALLOYS Herbert L. Eiselstein and John Gadbut, Huntington,

W. Va., assignors to The International Nickel Company, Inc, New York,N.Y., a corporation of Delaware N Drawing. Filed July 2, 1963, Ser. No.292,493 6 Claims. (Cl. 75-170) The present invention relates tohigh-nickel alloys and, more particularly, to high-nickel alloys havingan improved combination of properties, including strength andconductivity.

Heretofore, the art has endeavored to provide alloys for use in manyfields, such as in nuclear pOWer plants, rocket engines, aircraft enginefuel and oil coolers, compact heat exchangers and the like, which wouldhave satisfactory strength in the annealed condition while stillretaining a high heat conductivity. Pure copper has excellent heatconductivity but in the annealed condition the strength of this metal isso low it is not of practical engineering interest for such uses. Highlypure nickel (99.97% nickel) has a coefficient of heat conductivity ofabout 600 B.t.u./hr./ft. /in./ F., and a yield strength in the annealedcondition of only about 14,000 pounds per square inch (p.s.i.).Commercial Wrought nickel (99.5% nickel) has a coeflicient of heatconductivity of about 400 B.t.u./hr./ft. /in./ F. and a yield strengthin the annealed condition of about 20,000 p.s.i. Various alloys ofnickel and copper, e.g., 70:30 cupronickel, find considerableengineering usage. While 70:30 cupronickel has a yield strength of about18,000 p.s.i. in the annealed condition, the coefficient of heatconductivity is only about 200 B.t.u./hr./ft. /in./ F. Variousnickel-chromium alloys, e.g., an alloy containing about 80% nickel,about 14% chromium, and about 6% iron, have a-greatly improved yieldstrength on the order of about 30,000 p.s.i. in the annealed conditionbut such alloys have poor conductivity such that the coefficient of heatconductivity is only about 100 B.t.u./hr./ft. /in./ F. A need hasaccordingly existed in the art for an alloy which would havesubstantially improved strength in the annealed condition but whichwould still have a coefiicient of heat conductivity approaching that ofpure nickel. Although attempts were made to overcome the foregoingdifiiculties, none, as far as we are aware, was entirely successful whencarried into practice commercially on an industrial scale.

It has now been discovered that a special high-nickel alloy has amarkedly improved yield strength in the annealed condition as comparedto nickel of commercial purity While retaining to a marked extent theheat conductivity of nickel.

It is an object of the present invention to provide a high-nickel alloyhaving an improved combination of properties.

Another object of the invention is to provide a highnickel alloy havingimproved strength as compared to pure nickel and commercially availablenickel alloys.

The invention also contemplates providing a highnickel alloy havingimproved strength while retaining to a marked extent the conductivity ofnickel.

It is a further object of the invention to provide a highnickel alloyuseful for the production of articles such as condenser andheat-exchanger tubing, which articles have adequate strength andsatisfactory heat conductivity.

Other objects and advantages will become apparent from the followingdescription.

Generally speaking, the present invention contemplates providing ahigh-nickel alloy containing at least about 1% but not more than about7.5% columbium, about 3,303,022 Patented Feb. 7, 1957 ice 0.07% to about1% carbon, e.g., about 0.1% to about 1% carbon, with the ratio ofcolumbium content to carbon content being about 6:1 to about 25:1, andwith the balance of the alloy, except for minor amounts of incidentalelements and impurities not exceeding a total of about 1.75%, beingessentially nickel. The alloys are characterized by a yield strength inthe fully annealed conditionot at least about 27,000 p.s.i. and by acoefficient of heat conductivity of at least about 300 B.t.u./ hr./ft./in./ F.

In carrying the invention into practice, it is advantageous to employalloys containing about 1.2% or 1.4% to about 3.5% columbium, about 0.2%to about 0.4% carbon, with the ratio of columbium content to carboncontent being about 6:1 to about 15:1, and the balance, except for minoramounts of incidental elements and impurities not exceeding about 1.75%,being essentially nickel. Even more advantageously, the columbium tocarbon ratio is at least about 7: 1. These alloys are characterized by ayield strength in the annealed condition of at least about 40,000 p.s.i.and by a thermal conductivity coefficient of at least about 300B.t.u./hr./ft. in./ F.

The ranges of columbium content and carbon content and the ratio ofcolumbium content to carbon content as set forth hereinbefore are allimportant and these requirements must all be met in order to obtain thecombinations of strength and conductivity contemplated in the specialnickel alloys provided in accordance with the invention. When any ofthese requirements is not met, the properties of the resulting alloysare unsatisfactory from the standpoints of strength and/or conductivity.In addition, when the columbium to carbon ratio is less than 6:1 thereis a detrimental tendency toward the formation of graphite in theresulting alloy. For example, an alloy containing 0.20% carbon, 1.15%columbium, 0.5% iron, 0.27% manganese, 0.01% titanium, 0.048% magnesium,0.029% zirconium, balance nickel, and having a columbium to carbon ratioof 5.75 developed graphite after a 1600" F. anneal and had acomparatively low room temperature yield strength of 29,300 p.s.i. witha thermal conductivity of 334 whereas comparable Alloy 3, containing0.24% carbon and having a columbium to carbon ratio of 7.25, developedno graphite and had a yield strength of 56,300 p.s.i. under the sameconditions. Furthermore, alloys containing carbon contents less than0.07% 'develop unsatisfactory strength. Thus, an alloy containing 0.04%carbon, 0.03% manganese, 0.66% iron, 0.33% titanium, 1.63 columbium,balance nickel, when tested at room temperature, had a low yieldstrength of 20,600 p.s.i. (0.2% ofi set), a tensile strength of 76,200p.s.i., an elongation of 60%, a reduction in area of and a thermalconductivity of 316. Zirconium has a strengthening effect in the alloyand may be employed in amounts up to about 0.1%. The alloy may containincidental elements and impurities such as up to about 1.25% iron, up toabout 1% titanium, up to about 1% manganese, up to about 0.1% silicon,up to about 0.2% copper, and minor amounts of residual deoxidizers suchas mangnesium, calcium, cerium, aluminum, etc., in a total amount notexceeding about 0.1%. Elements such as chromium, molybdenum, tungstenand vanadium are detrimental impurities and should be substantiallyabsent from the alloy, i.e., should not be present in amounts exceedinga total of about 0.5 Other detrimental impurities such as sulfur,phosphorus and lead should be limited to a maximum of about 0.01%sulfur, about 0.01% phosphorus, and about 0.001% lead. Incidentalelements and impurities reduce the conductivity of the alloy withoutappreciable increase in the strength thereof and should not be presentin total amounts exceeding 3 about 1.75% and preferably should not bepresent in amounts exceeding about 0.5%.

A series of alloys in accordance with the invention were prepared by airmelting the constituents in an induction furnace. The molten metal ineach case was cast into ingots which were then forged into bars. Thechemical composition of the melts is set forth in the following Table I:

resistance welding, etc., may be employed in joining parts made of thealloys provided in accordance with this invention.

Thermal conductivity values reported herein for alloys within theinvention were determined in accordance with the method described byMorris E. Fine in Transactions A.I.M.E., volume 188, July 1950, pages951 and 952.

Although the present invention has been described in TABLE I Alloy N 0.Percent Percent Percent Percent Percent Percent Percent Percent PercentFe Mn Ti Mg Zr Ob/C Ni 0.28 0. 12 0. 01 0. 03 0. 040 0. 01 3. 05 I 10. 913:11. 0. 1. 11 0.30 0. 02 0. 024 0. 043 3. 12 12. 5 Hal. 0. 24 0. 68 0.26 0. 01 0. 022 0. 041 1. 74 7. 25 Bal. 0. 32 0. 06 0. 25 0. 03 0. 0430. 038 2. 87 8. 07 Bal. 0.26 O. 87 0.30 0. 02 0. 043 0. 036 2. 28 8. 8Bal. 0. 17 0. 84 0.29 0. 03 0. 025 0. 028 2. 22 '13. 0 Bal. 0. 87 0. 050. 19 0. 05 7. 29 8. 4 Bal. 0. 1.11 0.29 0.02 0. 026 0.021 3.10 8. 9Bal. 0. 07 0. 10 0. 01 0. 42 0. 046 0. 01 1. 52 21. 8 B211. 0. 08 0. 740. 01 0, 44 0. 061 0. 01 1, 61 20. 1 Bal.

NOTE.Ihese melts contained about 0.01% to 0.10% silicon, about 0.02% to0.03% copper, and about 0.002%

to 0.006% sulfur.

Portions from the forged bars were annealed at 1600 F. for /2 hour. Theannealed bars were subjected to tensile tests at room temperature andthe thermal conductivity was established. Results ,of the tests are setforth in the following Table II:

conjunction with preferred embodiments, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit and scope of the invention, as .those skilled in the art willreadily understand. Such modifications and variations are considered tobe Alloys in accordance with the invention are thermally stable. Thus,annealed alloys do not increase in hardness or strength when subjectedto heat treatments designed to reveal age hardening, i.e., 16-hour heattreatments at a temperature in the range of 900 F. to 1600 F.

The alloys provided in accordance with the present invention areparticularly applicable to the manufacture of heat exchangers which arerequired to have high heat transfer rates, e.g., where the overall heattransfer coeificient is at least about 1000 B.t.u./hr./ft. F. Examplesof such devices include regeneratively cooled rocket thrust chambers,nuclear power plants, and heat exchangers in which boiling takes place,in-pile test thimbles, aircraft air conditioning equipment, jet enginefuel coolers and oil coolers, etc. The alloys are particularlyadvantageous for the manufacture of heat exchange elements havingprotruding surfaces, such as finned tubes and the like, as it is foundthat the heat transfer characteristics of such elements aresignificantly improved through the use therein of the alloys within thescope of this invention.

Alloys provided in accordance with the present invention may readily bejoined with any of the common brazing and welding techniques. Thus, theusual brazing methods employed for joining nickel alloys and the usualwelding methods which include arc welding, oxyacetylene welding, spotwelding, submerged arc welding,

within the purview and scope of the invention and appended claims.

We claim:

1. A nickel-base alloy consisting essentially of about 0.07% to about 1%carbon, at least about 1% to about 7.5% columbium, with the ratio ofcolumbium content to carbon content being about 6:1 to about 25:1, and

with the balance of the alloy, except for minor amounts of incidentalelements and impurities not exceeding a total of about 1.75%, beingessentially nickel.

2. The alloy according to claim 1 wherein the carbon content is at leastabout 0.1%.

3. A nickel-base alloy consisting essentially of about 0.2% to 0.4%carbon, about 1.2% to about 3.5% columbium, with the ratio of columbiumcontent to carbon content being about 6:1 to about 15:1, and with thebalance of the alloy, except for minor amounts of incidental elementsand impurities not exceeding a total of about 1.75%, being essentiallynickel.

4. The alloy according to claim 3 wherein the columbiurn content is atleast about 1.4%.

5. The alloy according to claim 4 wherein the ratio of columbium contentto carbon content is at least about 7: 1. i

6. As a new article of manufacture, a heat exchanger comprised of thealloy defined in claim 1.

(References on following page) References Cited 1ay the Examiner 652,06110/1937 Gergany.

UNITED STATES PATENTS 614,349 12/1948 Great Britain. 1,355,532 V1920Brace DAVID L. RECK, Primary Examiner. 5 WINSTON A. DOUGLAS, Examiner.FOREIGN PATENTS c. M. SCHUTZMAN, R. o. DEAN,

616,858 8/1935 Germany. Assistant Examiners.

1. A NICKEL-BASE ALLOY CONSISTING ESSENTIALLY OF ABOUT 0.07% TO ABOUT 1%CARBON, AT LEAST ABOUT 1% TO ABOUT
 7. 5% COLUMBIUM, WITH THE RATIO OFCOLUMBIUM CONTENT T0 CARBON CONTENT BEING ABOUT 6:1 TO ABOUT 25:1, ANDWITH THE BALANCE OF THE ALLOY, EXCEPT FOR MINOR AMOUNTS OF INCIDENTALELEMENTS AND IMPURITIES NOT EXCEEDING A TOTAL OF ABOUT 1.75%, BEINGESSENTIALLY NICKEL.